Definition & Facts for Irritable Bowel Syndrome

What is IBS?

Irritable bowel syndrome (IBS) is a group of symptoms that occur together, including repeated pain in your abdomen and changes in your bowel movements, which may be diarrhea, constipation, or both. With IBS, you have these symptoms without any visible signs of damage or disease in your digestive tract.

IBS is a functional gastrointestinal (GI) disorder. Functional GI disorders, which doctors now call disorders of gut-brain interactions, are related to problems with how your brain and your gut work together. These problems can cause your gut to be more sensitive and change how the muscles in your bowel contract. If your gut is more sensitive, you may feel more abdominal pain and bloating. Changes in how the muscles in your bowel contract lead to diarrhea, constipation, or both.

Does IBS have another name?

In the past, doctors called IBS colitis, mucous colitis, spastic colon, nervous colon, and spastic bowel.

Are there different types of IBS?

Three types of IBS are based on different patterns of changes in your bowel movements or abnormal bowel movements. Sometimes, it is important for your doctor to know which type of IBS you have. Some medicines work only for some types of IBS or make other types worse. Your doctor might diagnose IBS even if your bowel movement pattern does not fit one particular type.

Many people with IBS have normal bowel movements on some days and abnormal bowel movements on other days.

IBS with constipation (IBS-C)

With IBS-C, on days when you have at least one abnormal bowel movement

more than a quarter of your stools are hard or lumpy and

less than a quarter of your stools are loose or watery

IBS with diarrhea (IBS-D)

In IBS-D, on days when you have at least one abnormal bowel movement

more than a quarter of your stools are loose or watery and

less than a quarter of your stools are hard or lumpy

IBS with mixed bowel habits (IBS-M)

In IBS-M, on days when you have at least one abnormal bowel movement

more than a quarter of your stools are hard or lumpy and

more than a quarter of your stools are loose or watery

How common is IBS?

Studies suggest that about 12 percent of people in the United States have IBS.1

Who is more likely to develop IBS?

Women are up to two times more likely than men to develop IBS.1 People younger than age 50 are more likely to develop IBS than people older than age 50.2

Factors that can increase your chance of having IBS include:

having a family member with IBS

a history of stressful or difficult life events, such as abuse, in childhood

having a severe infection in your digestive tract